Part 1, 1922] AMBROSIACEAE 21 
17. Ambrosia hispida Pursh, Fl. Am. Sept. 743. 1814. 
Ambrosia crithmifolia DC. Prodr. 5: 525. 1836. 
Ambrosia maritima Ferrero; DC. Prodr. 5: 525, asasynonym. 1836. 
A suffruticose perennial, branched at the base; branches prostrate, often rooting at the 
nodes, 2-8 dm. long, terete, densely white-pilose or white-hirsute; leaves tripinnatifid or the 
upper bipinnatifid, hispid-villose on both sides; petioles 1-3 em. long; blades broadly ovate in 
outline; segments spreading, not decurrent, the ultimate ones oblong or obovate, obtuse, min- 
ute, entire or dentate; staminate heads rather few, in dense terminal racemes; peduncles about 
2 mm. long; involucre saucer-shaped, 4-5 mm. broad, hispidulous, crenate; paleae of the re- 
ceptacle linear-filiform, clavate and hairy towards the end; corolla pilose at the apex; pistillate 
heads in small clusters in the upper axils; body of the fruit about 3 mm. long, obovoid, ob- 
scurely 4-angled, hirsute and glandular; beak conic, about 1.5 mm. long; spines 1—5, unequal, 
conic. 
TYPE LocaALity: Given as South Carolina, but probably the Bahamas. 
DISTRIBUTION: Subtropical Florida; Bahamas; Cuba to Barbados; Yucatan; Panama; intro- 
duced in British Guiana. 
ILLUSTRATIONS: Field Mus. Publ. Bot. 3?: 287. 
18. Ambrosia velutina O. E. Schultz, Symb. Ant. 7: 88. 1911. 
A suffruticose perennial, with a branched root; stem 3-5 dm. high, terete, grayish and 
softly pubescent; leaves mostly opposite, bipinnatifid, densely and softly pubescent on both 
sides greenish above, canescent beneath; petioles 1-1.5 cm. long; leaf-blades triangular-ovate, 
about 4 cm. long; primary segments lanceolate, the secondary ones ovate; staminate heads 
numerous, in terminal racemes; peduncles 1-2 mm. long; involucre 3 mm. broad, about 15- 
flowered, saucer-shaped or hemispheric, softly pubescent, crenate; paleae of the receptacle 
filiform, slightly clavate and puberulent at the apex; corollas puberulent; pistillate heads in 
clusters of 3-5 in the upper axils; body of the fruit about 2 mm. long, ovate, canescent 
when young; beak about 0.5 mm. long; spines small. 
TYPE LOCALITY: Haiti. 
DISTRIBUTION: Cuba and Hispaniola. 
19. Ambrosia trifida L. Sp. Pl. 987. 1753. 
? Ambrosia simplicifolia Walt. Fl. Car. 231. 1788. 
Ambrosia integrifolia Muhl.; Willd. Sp. Pl. 4: 375. 1805. 
Ambrosia trifida integrifolia T. & G. Fl. N. Am. 2: 290. 1842. 
Ambrosia trifida heterophylla Kuntze, Rev. Gen. 305. 1891. 
A tall annual; stem 1-5 dm. high, scabrous-hispidulous and somewhat hirsute; leaves 
deeply 3-cleft or the lower 5-cleft, or many of the upper or sometimes all entire; petioles 5-15 
cm. long, more or less winged and hirsute-ciliate; leaf-blades usually rhombic in outline or if 
entire ovate; lobes ovate or lanceolate, acuminate and serrate; staminate heads numerous, 
paniculate or racemose; involucre saucer-shaped, 3 mm. wide, with 6-8 rounded lobes, with 3, 
rarely 4, blackish ribs on the upper side, hispidulous on the portion between them, otherwise 
glabrous; corolla glabrous with some or all of the angles blackish; paleae of the receptacle 
rudimentary, bristle-like; pistillate heads in small clusters at the base of the staminate racemes, 
subtended by 3-cleft bracts which usually have two black veins, one in each of the lateral 
lobes; body of the fruit about 5 mm. long, obovoid, with 6-7 ridges and as many conic short 
spines, faintly, if at all, pitted, but often with dark-purple streaks between the ridges; beak 
conic, about 2 mm. long. 
TYPE LOCALITY: Virginia. 
DISTRIBUTION: Quebec to Florida, Colorado, and eastern British Columbia. 
ILLUSTRATIONS: Britt. & Brown, Ill. Fl. f. 3592; ed. 2.f.41206; Clark & Fletcher, Farm Weeds 
een up 23; pl. 55, f. 57; ed. 2, pl. 56; pl. 75, f. 78; Clark & Fletcher, Mauv. Herbes Can. 1. 23; pl. 
ines 
20. Ambrosia aptera DC. Prodr. 5: 527. 1836. 
Ambrosia trifida texana Scheele, Linnaea 22: 156, 1849. 
A tall annual, 1-5 m. high; stem angled, striate and scabrous; lower leaves deeply 5-cleft, 
the upper 3-cleft or simple, scabrous on both sides; petioles 5-15 cm. long, wingless; leaf-blades 
